In recent years, for example in semiconductor devices fabricated by electron-beam lithography, lithography patterns with high-resolution have been required high positional precision along with improvement in a high degree of integration of the semiconductor devices. Electron-beam lithography system is a system in which an electron beam is focused with an electron lens and deflected with a deflector while moving the sample, to draw high-resolution patterns on a sample with high positional precision. The positional precision is required in nanometers.
The coefficient of linear expansion of a silicon is 4×10−6[1/K]. Therefore, the sample whose diameter is 300 mm expands 1.2 nm by an increase of 1/1000° C. in the temperature of the sample. Likewise, since the coefficient of linear expansion of a ceramic is 3×10−6[1/K], the ceramic structural member expands 0.9 nm by an increase of 1/1000° C. in the temperature of the ceramic. Consequently, in order to suppress an error (the thermal distortion) dependent on an ambient temperature to 1 nm, the sample and stage structural must be kept temperature-stable despite a thermal variation change in temperature of 1/1000° C.
Heat dissipated during lithography includes heat dissipated from an electrostatic chuck, rolling frictional heat dissipated from a stage guide, and heat dissipated from a motor. However, such heat is hardly released in a sample chamber because the chamber is held vacuum. According to a conventional technology, a coolant is circulated around a stage to keep the temperature of a sample constant. However, since a long time constant is required until heat is conveyed to a structural member after adjusting the temperature of the coolant. Consequently, the temperature of a top table at the stage or the temperature of the sample deviates by a few hundredth of a degree C.
Japanese Patent Laid-Open No. 2002-353116 (Patent Document 1) has disclosed a technology of placing heater wires on a stage and compensating a temperature of the sample by the passage of electric current through a heater wire during a period of time where lithography is not performed.
In addition, the above-Document 1 has described that a magnetic field, which is induced by the passage of electric current through the heater wire, have an adverse effect on electron-beam lithography (drawing) on a sample, and described how to prevent such a effect. Particularly in the Document 1, a heater wire having the same current-carrying capacities is disposed with turns in parallel, and current is fed through the turned heater wire potions in mutually opposite directions, whereby the adverse effect of the magnetic field is minimized.